Rhombohedral boron monosulfide as a metal-free photocatalyst

Most of previous photocatalysts contain metal species, thus exploring a metal-free photocatalyst is still challenging. A metal-free photocatalyst has an advantage for the development of economical and non-toxic artificial photosynthesis system and/or environmental purification applications. In this study, rhombohedral boron monosulfide (r-BS) was synthesized by a high-pressure solid-state reaction, and its photocatalytic properties were investigated. r-BS absorbed visible light, and its photocurrent action spectrum also exhibited visible light responsivity. The r-BS evolved hydrogen (H2) from water under ultraviolet (UV) as well as under visible light irradiation, and its internal quantum efficiency reached 1.8% under UV light irradiation. In addition to the H2 evolution reaction, the r-BS photocatalyst drove carbon dioxide (CO2) reduction and dye oxidation reactions under UV irradiation. Although bare r-BS was not so stable under strong light irradiation in water, cocatalyst modification improved its stability. These results indicate that r-BS is a new class of non-metal photocatalyst applicable for H2 production, CO2 reduction, and environmental purification reactions.

Light energy

Figure S13
The relationship between concentration of methylene blue in aquaeous solution and its optical absorbance at 664 nm.The hydrogen evolution experiment was conducted in small quartz cell.The light source of each wavelength was irradiated to r-BS dispersed in water with the addition of ethanol for 30 min.We calculate the IQE from the hydrogen evolution rate determined by the amount of hydrogen production for 30 min divided by absorbed photon numbers determined by the spectrum of the light source and absorption spectrum of r-BS as follows,

1.
Figure S1Schematic illustration for vibration modes of r-BS.

Figure S2
Figure S2Wide-scanned XPS spectra of r-BS on a graphite tape and of a bare graphite tape.

Figure S3
Figure S3 Linear sweep voltammogram of r-BS electrode under chopping light by a 150 W xenon lamp.

Figure S5
Figure S5The absorption spectra of MB dye for before and after light irradiation and those after O2 bubbling for 20 and 40 mins under dark condition.

Figure S6
Figure S6The result of durability test for hydrogen production under strong light condition.

Figure S7
Figure S7XRD patterns and UV-vis spectra of r-BS before and after long time irradiation.

Figure S8
Figure S8SEM images of as prepared r-BS and long time irradiated r-BS.

Figure S9
Figure S9XPS spectra for B-1s and S-2p orbitals before and after the photocatalysis test.

Figure S10
Figure S10Schematic illustration of a capsule for high-pressured r-BS synthesis.

Figure S11
Figure S11 Spectra of light sources which were used for photocatalyst experiments.

Figure
Figure S12 (a) A 65 mL reactor with a quartz window for light irradiation.Three septum parts are installed for gas injection and sampling.(b) a 4.5 mL quartz reactor with a septum cap.

Figure S13
Figure S13Relationship between concentration of methylene blue in aqueous solution and its absorbance at 664 nm.

Figure S1
Figure S1 Schematic illustration for vibration modes of r-BS.

Figure
Figure S2 Wide-scanned XPS spectra of r-BS on a graphite tape (blue line) and of a bare graphite tape (red line).

Figure S3
Figure S3 Linear sweep voltammograms of r-BS electrode on a carbon substrate (a) and bare carbon substrate (b) under chopping light by a 150 W xenon lamp.

Figure S6
Figure S6The result of durability test for hydrogen production under strong light condition.

Figure S7
Figure S7 XRD patterns (a) and UV-Vis spectra (b) of r-BS before and after irradiation.

Figure S8
Figure S8 SEM images of as prepared r-BS (a) and long time irradiated r-BS (b).

Figure S9
Figure S9XPS spectra of r-BS for B-1s (a) and S-2p (b) orbitals before the photocatalysis test.Panel (c) and (d) are the results of B-1s and S-2p after the photocatalysis test.As described in the experimental section of the manuscript, the charge build-up effect was calibrated by using the C-1s peak of a graphite tape (284.6 eV).Shifted values for the calibration were -2.5 eV and -2.8 eV for the samples before and after the photocatalysis test, respectively.

Figure S10 Figure S11
Figure S10Schematic illustration of a capsule for high-pressured r-BS synthesis.

Figure
Figure S12 (a) A 65 mL reactor with a quartz window for light irradiation.Three septum parts are installed for gas injection and sampling.(b) A 4.5 mL quartz reactor with a septum cap.